This invention relates to the production of organic compounds, especially hydrocarbons, from starting materials such as methanol, dimethyl ether, and mixtures thereof. More particularly, the invention provides a novel process for the production of branched chain hydrocarbons, particularly triptane, from either methanol, dimethyl ether, or mixtures thereof.
Prior experimental work with methanol conversion to hydrocarbons may be characterized as largely academic or substantially un-economic in present terms. For example, as early as 1878, LeBel and Greene (Compt. rend. vol. 87, p. 260) produced alkyl hydrocarbons by contacting methanol with zinc chloride at elevated temperatures. More recently, Grosse and Snyder describe and claim a process in U.S. Pat. No. 2,492,984 wherein a mixture consisting essentially of a specified metal halide and at least one compound selected from the group consisting of methanol and dimethyl ether is subjected to conversion conditions, including a temperature of 250.degree. to 650.degree. C, to form substantial amounts of recoverable hydrocarbons having at least four hydrocarbons. The examples of the patent employ a zinc chloride catalyst, and the specification mentions that higher atomic weight halides of metals such as zinc, cadmium, thorium, and the like, may be used.
However, results reported in the patent are far from satisfactory, insofar as disclosure of suitable yields of high grade gasoline components is concerned. Conversions of up to 50 percent of recoverable hydrocarbons of four carbon atoms, based on the mols of methanol or dimethyl ether converted, are claimed. However, the experiments disclosed report, at best, a fraction containing about 20 percent (on the same basis) of recoverable hydrocarbon material boiling between 25.degree. C at atmospheric pressure and 85.degree. C at 1.5 mm. of Hg pressure (about 246.degree. C at atmospheric pressure). No mention is made of the production of triptane (2,2,3-trimethyl butane), a heptane and a valuable fuel component.
The high cost of petroleum-based fuels and the potential availability of large quantities of methanol, e.g., methanol derived from synthesis gas or methane, have given rise to efforts to convert this methanol into higher grade fuels. Because of the superiority of triptane as a blending agent for high-grade gasoline, a process for producing triptane, as well as other hydrocarbons, from methanol or dimethyl ether could have great economic importance.